<template>
  <div>
    <router-link 
    tag="div" 
    to="/" 
    v-show="showAbs"
    class="header-abs">
      <span class="iconfont header-abs-back">&#xe618;</span>
    </router-link>
    <div class="header-fixed" 
        :style="opacityStyle"
        v-show="!showAbs">
      <router-link to="/">
        <div class="header--fixed-left iconfont">&#xe618;</div>
      </router-link>{{this.title}}
    </div>
  </div>
</template>

<script>
export default {
  name: "DetailHeader",
  props:{
    title:{
      type:String,
      default:''
    }
  },
  data () {
      return {
          showAbs: true,
          opacityStyle: {
              opacity: 0
          }
      }
  },
  methods: {
      handleScroll () {
        const top = document.documentElement.scrollTop
        if(top > 60) {
            let opacity = top / 140
            opacity = opacity > 1 ? 1 : opacity
            this.opacityStyle.opacity = opacity
            this.showAbs = false
        }else {
            this.showAbs = true
        }
      }
  },
  activated () {
      window.addEventListener('scroll',this.handleScroll)
  },
  deactivated () {
      window.removeEventListener('scroll',this.handleScroll)
  }
};
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl';

.header-abs {
  position: absolute;
  left: 0.2rem;
  top: 0.2rem;
  width: 0.8rem;
  height: 0.8rem;
  line-height: 0.8rem;
  border-radius: 0.4rem;
  text-align: center;
  background: rgba(0, 0, 0, 0.8);

  .header-abs-back {
    color: #fff;
    font-size: 0.4rem;
  }
}

.header-fixed {
  position: fixed;
  z-index: 2
  top: 0;
  left: 0;
  right: 0;
  text-align: center;
  line-height: $headerHeight;
  height: $headerHeight;
  background: $bgColor;
  color: #fff;
  font-size: 0.32rem;

  .header--fixed-left {
    position: absolute;
    left: 0;
    top: 0;
    width: 0.64rem;
    float: left;
    color: #fff;
  }
}
</style>